Many vehicles include antilock brake control as a standard feature. The primary inputs to a typical antilock brake control are the wheel speed signals output by sensors that monitor the rotational velocities of the vehicle wheels. In some vehicles, the antilock brake control controls the rear wheels together and can rely on an average of the rear wheel speeds. For example, in a rear-wheel-drive or four-wheel-drive light truck in which the antilock brake control controls the rear wheels together, the average rear wheel speed may be taken from the transmission output shaft driving the rear wheels.
Light duty trucks make good candidates for electric conversion vehicles because they have plenty of room and load capacity for batteries and they are useful to many operators who could use an electric conversion vehicle. During the conversion to an electric vehicle, the internal combustion engine and drive train are removed and replaced with an electric motor and drive train. The electric drive train may be only front wheel drive. In these vehicles, there is no output shaft to drive the rear wheels, so the average rear wheel speed signal that was provided by the output shaft is no longer available.